Surge arresters for voltages of the of the above-mentioned order of magnitude can be subjected to high mechanical stresses, for example due to wind load and earthquake.
It is known to design surge arresters for high system voltages with a lower part comprising three vertically arranged insulator columns, which are mounted at the bottom on a metal stand intended for ground connection to form, in cross section, an equilateral triangular configuration. The lower part supports a centrally placed upper insulator column, which at the top is provided with an end armature intended for high-voltage connection. Each insulator column is composed of a plurality of coaxially arranged hollow insulators of porcelain. The upper insulator column and one of the insulator columns in the lower part comprise varistor blocks, whereas the other two insulator columns in the lower part are empty and only have a mechanical function. Such an arrester, designed for system voltages of 1600 kV, is shown in Asea Journal 1977, vol. 1, p. 19. This arrester has a height of 13 meters. Such a design is very costly and, in addition, cannot be used without taking special measures if the housings of the valve units are made of polymer material instead of porcelain, because these materials have completely different mechanical properties.